Check Out How the Ferrari Purosangue SUV’s Active Suspension Works

2023-03-08 14:00:43 By : Mr. Mison Wong

Automotive engineers have long teased us with the idea of a car that doesn't just absorb jolts, but that actively compresses and extends its suspension to smooth out bumps and tame body motions. Most famously, Bose blew minds in 2004 when it showed off a Lexus LS400 that could weave through a slalom, float over undulations, and brake to a stop while keeping its body almost perfectly flat. With 24 years of development invested in its electromagnetic active suspension, Bose could even jump the Lexus over a 2-by-6 standing on its edge. The fact the technology never reached production doesn't stop people from talking about the Bose active suspension today as if it was the greatest invention since the horseless carriage.

The electric motors built into the dampers of the $393,350 2024 Ferrari Purosangue offer the same basic promise as the Bose system and every other active suspension: to simultaneously improve ride quality and handling dynamics. If Ferrari engineers wanted, they could have eliminated body roll or even leaned their SUV into corners with their new trick shocks, but the Purosangue isn't that kind of show pony. Controlled body roll provides critical feedback to the driver, and Ferrari's first production four-door has big shoes to fill when it comes to driver engagement. An active suspension helps the Purosangue deliver the practical comfort of a four-door utility vehicle and the agility of Ferrari's legendary supercars.

Don't confuse Ferrari's active suspension with the air springs or adaptive dampers found in so many modern cars. Air springs are slow-acting devices that can adjust ground clearance and spring rates for different driving modes. Adaptive dampers make a suspension stiffer or softer by electronically adjusting the valving or, in the case of Magnetic Ride Control, altering the viscosity of hydraulic fluid inside them. All of these are passive devices, capable only of dissipating the energy transmitted into the suspension.

An active suspension can generate a force that causes the vehicle body to move relative to the wheels. These motions can be used to soften impacts, lower the vehicle's center of gravity, shift the load carried by each tire, and minimize or even eliminate body roll and pitch.

The 2024 Ferrari Purosangue's active suspension is powered by four high-tech dampers developed by Multimatic, the chassis wizards that democratized spool-valve dampers and gave us the Ford GT's brilliant two-stage pushrod suspension. These Multimatic TrueActive Spool Valve dampers are each fitted with a liquid-cooled 48-volt motor geared to a ball screw mechanism that transmits up to 1,120 pounds of force to the damper shaft. A liquid-cooled motor control module on each damper takes orders from a central chassis controller that considers inertial sensors, slip angle, and vehicle speed.

As the name suggests, Multimatic's TASV dampers also pump hydraulic fluid through spool valves as the suspension strokes. This passive damping works in parallel with the electric motors to quench impacts and heaves. The spool valves also calm the high-frequency secondary ride motions that are too fast to be controlled by the electric motors.

The Ferrari Purosangue SUV has no anti-roll bars, and its steel coil springs are softer than if they had been paired with adaptive or non-adjustable dampers. This setup favors ride comfort as the default while the active dampers ratchet up the stiffness for body control as needed.

Ferrari says the whole system adds 99 pounds over typical adaptive dampers. A little more than half of that mass is unsprung weight carried on the dampers. The rest of the hardware, including a 48-volt battery, resides within the body.

The motors make adjustments every 0.05 second, pulling the wheels and body closer together or pushing them further apart. It's easy to imagine how this can improve ride quality. While the Purosangue can't read the road ahead, as soon as the accelerometers sense a suspension event, the active dampers can help a wheel over a bump to reduce how much of that motion transmits into the cabin.

The active dampers also pull the body toward the wheels under braking and cornering to drop the Purosangue's center of gravity closer to the road. A lower center of gravity reduces load transfer from the inside tires to the outside tires, which in turn increases grip. Note that this feature isn't a substitute for air springs, as it's only used during dynamic maneuvers. Activating launch control is the only way to lower the car while stationary, as the crouched stance offers better traction off the line. And while the motors could theoretically also be used to raise the ground clearance, Ferrari offers no such feature. The company might be open to building a four-door SUV, but based on what this suspension is designed to do, it's clear Ferrari isn't interested in making an off-roader.

To fully appreciate how the active dampers affect the 2024 Ferrari Purosangue's handling, you have to understand one key point: As you raise and lower the body at each corner, you also shift how much weight each tire carries (this is a setup trick racing teams refer to as "crossweight"). That load ultimately determines how much grip a tire has to work with.

Shifting the weight among the four wheels allows Ferrari to actively change the Purosangue's front-to-rear roll stiffness distribution, one of the most important attributes in determining if a vehicle is an understeering pig, an oversteering trainwreck, or a beautifully balanced driver's car. Multimatic's dampers can redistribute the front-to-rear load by as much as 10 percent, allowing Ferrari to dynamically fine-tune the handling balance based on the driving mode, speed, and driver inputs.

The difference between the active suspension and the adaptive alternative isn't just in the subjective feeling. Ferrari says the active suspension is good for a 10 percent increase in lateral grip, while Multimatic says it trims 1.9 seconds off a 2-minute, 8-second road-course lap. If only it could hurdle a 2-by-6, too, more people might recognize the technology for how innovative it is.